The present invention relates in general to electronic circuits and, more particularly, to amplifying circuits that operate at low supply voltage levels.
As integrated circuits achieve higher levels of integration, there is a corresponding need to operate the circuits at reduced voltage levels in order to maintain power dissipation at manageable levels. For example, it is anticipated that future microprocessors and other digital circuits will need to operate with power supply voltages of 0.5 volts to maintain an acceptable die temperature. Future circuits are expected to operate with even lower supply voltages.
A low supply voltage typically is produced by a voltage regulator implemented as an integrated circuit. The regulator includes an error amplifier to sense the supply voltage and feed back an error signal that adjusts the voltage level to maintain regulation. The error amplifier and its associated circuitry preferably also operate at a low voltage in order to achieve a low power dissipation by the regulator circuit.
Most if not all integrated circuit amplifiers operate only at supply voltages that exceed the conduction threshold of the integrated circuit""s transistors. When the supply voltage drops below the conduction threshold level, the transistors cease to function and gain of the amplifiers drops quickly to zero. In a case where the amplifier is being used in a voltage regulator, the rapid loss of gain can cause the regulator""s output voltage to transition out of its specified range, which can damage both the regulator and the circuits operating from the regulator""s output supply voltage.
Accordingly, there is a need for an amplifier circuit and method of amplifying that maintains functionality at lower supply voltages than what is currently available.